Paris Métro helps heat low-income housing

Seventeen apartments in a public housing block in Paris will draw heat from the metro.

The Paris Métro is hot -- literally. In 1956, when the cars on line 11 Châtelet - Mairie des Lilas were fitted with rubber tires for better traction to grip the rails on the line's steep grades, the byproduct was heat and plenty of it. And then there is the body heat given off by the subways riders. An estimated 6 million passengers a day ride the Paris Métro, and each of them gives of some 100 watts of heat, according to Francois Wachnick, a spokesman for Paris Habitat OPH, the largest owner of social housing units in the city. The waste heat is enough to keep the Rambuteau Métro station at a sultry 14 - 20 C year-round. Now Paris Habitat OPH, wants to capture some of that warmth to help heat a low-income housing block near Rambuteau station in central Paris.

Heat exchangers will extract the warmth from the hot subway air and transfer it to water running through pipes, which will be led up to street level through an old stairwell, and into the under-floor heating system in the apartments. The existence of the stairwell connecting the apartment block to the subway eliminates the need for excavation to run the pipes into the metro tunnel. Without the stairwell, the project would have been prohibitively expensive. Paris Habitat OPH anticipates that the heat harvested from the metro will cut heating costs by up to a third. A call for tenders will be concluded by the end of the year and construction of the system is slated to begin in 2011.